D. ELECTRIC ORGANS. 



ELECTRIC organs are present in some Fishes, being most 

 strongly developed in certain Rays (Torpedinidae, e.g. Torpedo, 

 Hypnos) found in the Atlantic Ocean and various southern seas, 

 in a South American Eel (Gymnotus ekctricus) and in an African 

 Siluroid (Malopterurus eleetricus). Gymnotus possesses by far the 

 strongest electric power, next to it comes Malopterurus, and then 

 Torpedo. The electric batteries of these three Fishes are situated 



in different parts of the body : in 

 Torpedo they have the form of a 

 broad mass, extending throughout 

 the substance of that part of the 

 body lying between the gill-sacs 

 and the propterygium on either 

 side of the head (Fig. 142); in 

 Gymnotus they lie in the ventral 

 region of the enormously long tail 

 (Fig. 143), that is, in the position 

 usually occupied by the ventral por- 

 tion of the great lateral muscles; 

 and finally, in Malopterurus, the 

 electric organ extends between the 

 skin and muscles round almost the 

 entire circumference of the body, 

 thus enclosing the Fish like a 

 mantle: it is especially strongly 

 developed along the sides, but is 

 separated by the branchial apparatus 

 into dorsal and ventral portions. 



The electric power of those 

 Fishes which were formerly known 

 as " pseudo-electric " has now been 

 fully demonstrated, though it is 

 much feebler than in the forms described above. To this category 

 belong, e.g. all the Rays, excluding Torpedo, and the various 

 species of Mormyrus and Gymnarchus (both belonging to the 

 Teleostei). In all these the electric organs lie on either side of the 

 end of the tail and have a metameric arrangement like that of the 

 caudal muscles ; in the Mormyridse, for example, there is on either 



FIG. 142. Torpedo marmorata, 

 WITH THE ELECTRIC ORGANS (E) 



EXPOSED. 



A u, eye ; KK, gill clefts ; S, skull ; 

 Sp, spiracle. 



